Chapter 7 Word File - c|net

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The Internet

and Intranets


1.

Briefly describe how the Internet works, including alternatives for connecting to it, and
the role of the TCP/IP protocol


2.

Identify and briefly describe five services associated with the Internet



3.

Describe the World Wide Web, including tools to view and search the Web


4.

Outline the process for creating Web content


5.

Describe Java and discuss its potential impact on the software world



6.

Define the term intranet and discuss how organizations ar
e using intranets


7.

Identify several issues associated with the use of networks

Use and Functioning

of the Internet

The Internet



The world’s largest computer network



Consists of thousands of interconnected networks



ARPANET: Ancestor of the Internet



Started by the Department of Defense to link DOD & military research
contractors



Split into two networks



MILNET: all military sites



Reduced ARPANET: non
-
military sites

The Internet

How the Internet Works

The

Internet transmits data from one computer (host) to another.

How the Internet Works



Messages are routed through the multiple networks that make
up the Internet by using special protocols.



Internet Protocol (IP)



The set of conventions used to pass packets from one host to another



Transport Control Protocol (TCP)



Used in connection with IP



Operates at the transport layer

How the Internet Works



Each computer on the Internet has an assigned address to
i
dentify it from other hosts (e.g., 123.45.67.89).




Most also have names, which are much easier to remember
than the numbers (e.g, flash.acme.com).

Internet Zones



com
: commercial sites



edu
: educational sites



mil
: military sites



gov
: government sites



net
: networking organizations



org
: organizations



firm
: businesses/firms



store
: businesses offering goods for purchase



info
: information service providers



web
: entities related to World Wide Web activities



arts
: cultural and entertainment activities



rec
: recreational activities



nom
: individuals

Three Ways

to Access the Internet



Connect via LAN server




Connect via SLIP/PPP




Connect via an on
-
line service

Three Ways

to Access the Internet

Requirements for

Connecting via LAN Server



Network adapter card



Open Datalink Interface (ODI) or Network Driver Interface
Specification (NDIS)



Communications

stack



Software that provides a set of communications protocols that
perform the compl
ete functions of the seven layers of the OSI
communications model

A Communications Stack for Accessing the
Internet

Requirements for

Connecting via SLIP/PPP



Modem and the TCP/IP protocols




Serial Line Internet Protocol (SLIP) or Point to Point Prot
ocol
(PPP) software (communications protocols that transmit packets
over telephone lines, allowing dial
-
up access to the Internet)

Requirements for Connecting via an On
-
Line
Service



Modem




Standard communications software




On
-
line information ser
vice account

Sample On
-
Line Service

Internet Services

Internet Services

Electronic Mail (E
-
Mail)



A way of sending an electronic message between individuals or
computers




Often called a
store and forward
system



Allows e
-
mail to be stored until it can be forwarded to the next
computer

Electronic Mail (E
-
Mail)



Typical e
-
mail message includes:



“From” line



“To” line



“Subject” line



“Message”

Usenet and Newsgroups



Usenet



A system closely allied wit
h the Internet that uses e
-
mail to provide a
centralized news service




Newsgroup



An on
-
line discussion group that focuses on a particular topic

Sample Newsgroup:

Sewing Newsgroup

Finding Information and Downloading Files



Telnet



A terminal emulation protocol that lets a user log on to another
computer on the Internet to gain access to publicly available files




File Transfer Protocol (FTP)



Describes the file transfer process between a host and a remote
computer

Internet Phone

and Videoconferencing Services



Internet phone service



Enables users to communicate with other Internet users around the
world who have compatible equipment and software




Internet videoconferencing



Supports both voice and visual communications



An emerging service

The World Wide Web

World Wide Web



Involves over 30,000 independently owned computers that work
together as one in an Internet Service




Also known as the Web, WWW, or W3




A menu
-
based system that uses the client/server model

World Wide Web



Data exists on the Web as:



ASCII characters



Word processing files



Audio files



Graphic images



Any other sort of data that is stored in a computer file

World Wide Web



A web site is like a magazine, with a cover page (
hom
e page)

that has graphics, titles, and black and blue text.



Hypertext
: Blue, underlined type which links the on
-
screen page to
other documents or Web sites



Hypermedia



Connects data on pages, allowing users to access topics in any order

World Wide

Web



Uniform Resource Locators (URLs)



A standard way of coding the location of the
Hypertext Markup
Language

(HTML)

documents




Hypertext Transfer Protocol (HTTP)



A set of rules that allows the Web user to retrieves a document

Sample Web Site:

The Wall Street Journal

Sample Web Site:

Center for Disease Control

World Wide Web



Hypertext Markup Language (HTML)



Standard page description language for Web pages



HTML tags



Codes that let the browser know how to format the text

Business Uses of the Web



In 1991, the Commercial Internet Exchange (CIX) Association
was established to allow businesses to fully connect to the
Internet.




Now businesses use the Internet for many applications:
E
-
mail, customer information web sites
, advertising direct sales
web sites, on
-
line shopping.

Web Browsers



A Web tool that creates a unique, hypermedia
-
based menu as a
graphical interface to the Web




Applets



Small programs embedded in Web pages

Search Engines



Web search tools that help users find the information they seek




Two types of Web search tools



Directories: List of Web sites classified by topic



Indexes: Allow users to find specific documents through keyword
searches

Sample Search Engine

Developing Web Content



Web authors work with several standards to create their pages.



Two main problems limit creativity.



Confusing HTML standards



Slow communications speeds



Virtual Reality Modeling Language (VRML)



A language for creating

3
-
D scenes on the Internet

Java



Object
-
oriented program language from Sun Microsystems
based on C++




Allows small programs (
applets)

to be embedded within an
HTML document

Downloading an Applet

from a Web Server

Web Page with a Java Applet

Intranets



Internal corporate networks built using Internet and World Wide
Web standards and products



Most companies have the foundation for an intranet: a network
that uses the Internet’s TCP/IP.



Next stage of intranet usage: Interactive transac
tion
-
based
applications

Common Intranet Uses

Net Issues

Managing the Internet

and Intranets



Although the Internet is a huge, global network, it is managed at
the local level; no centralized governing body controls the
Internet.




The Internet Society

and the Internet Activities Board (IAB) are
the closest things to centralized governing bodies.

Service Bottlenecks



Primary cause: phenomenal growth in traffic




Other causes



More than half of Web users have slow modems (14.4 Kbps or less)



Ine
fficient software and software glitches

Cryptography



The process of converting a message into a secret code and
changing the encoded message back into regular text




Digital Signature



A technique used to meet security needs for the processing of on
-
line
financial transactions

Cryptography

Firewalls



A device that sits between the internal network and the outside
Internet



Purpose: To limit access into and out of a network based on
an organization’s access policy



Can be set up to allow access from specific hosts and networks
or to prevent access from specific hosts

Information Systems Principles



The Internet is like many other new technologies
--

it provides a
wide range of ser
vices, some of which are effective and
practical for use today, whereas others are still evolving, and
still others will fade away from lack of use.

Information Systems Principles



People need improved means to communicate and collaborate
--

thus the pop
ularity of the Internet and other technology and
services that can make this happen.

Information Systems Principles



As with every new technology, the Internet and corporate
intranets are experiencing growing pains. Standards are
needed, options must b
e sorted out, financial transactions must
be made secure, privacy must be guaranteed, and legal issues
must be addressed.

Information Systems Principles



The Java approach to delivering software to users is so radically
different from current approaches that it will drive major
changes in the software industry.

End of Chapter 7